When producing peptides using genetic recombinant technology, peptides are frequently expressed in the form of a fusion protein because peptides are prone to be decomposed inside the cell. Well-known methods of excising a target peptide from a fusion protein include chemical cleavage using bromcyan (Itakura, et al., Science, 198, 1056 (1977)), and enzymatic cleavage using factor Xa (Nagai, et. al., Methods in Enzymology, 153, 46(1987)).
Further, a well-known method of cleaving the peptide bond in a protein is to cleave the acyl cysteine bond using 2-nitro-5-thiocyanobenzoic acid (“Course on Biochemical Experiments” 1, Protein Chemistry II, Japan Biochemistry Society, ed., published by Tokyo Chemists, pp 247-250, 1976). Nonetheless, there has been no disclosure on excision of a target peptide from a protein.
When excising a target peptide from a fusion protein using conventional technology, the excision with bromcyan cannot be applied to the production of a peptide containing methionine, and has many problems on the yield of excision, etc.
In this way, it is desirable to have a method of efficiently cleaving a target peptide from a fusion protein or polypeptide.